Method and apparatus for the examination of articles for defects

ABSTRACT

A method for examining the upper part of a glass vessel for defects comprises the steps of applying a fluorescent material to selected surfaces of the upper part of the vessel while inhibiting the introduction of the fluorescent material into voids or defects existing in coated surfaces, irradiating the coated surface with light having a frequency for exciting the fluorescent material, scanning the surface for discontinuities occurring in fluorescent radiation which corresponds to defects in the vessel, and providing an indication of the existence of such a discontinuity. The selected surfaces, in particular, comprise helically formed threads and the top surfaces of screw top beverage bottle. An apparatus in accordance with the invention is provided for effecting the examination of a glass vessel.

United States Patent Snyder METHOD AND APPARATUS FOR THE EXAMINATION OFARTICLES FOR DEFECTS [76] Inventor: Ellery P. Snyder, Green Hill Rd,

[52] US. Cl. 250/302, 250/461 [51] Int. Cl. ..G01n 21/16 [58] Field ofSearch 250/302, 458, 461;

[451 Aug. 13, 1974 Primary Examiner-James W. Lawrence AssistantExaminer-Davis L. Willis Attorney, Agent, or Firm-Kaufman & Kramer 5 7ABSTRACT A method for examining the upper part of a glass vessel fordefects comprises the steps of applying a fluorescent material toselected surfaces of the upper part of the vessel while inhibiting theintroduction of the fluorescent material into voids or defects existingin coated surfaces, irradiating the coated surface with light having afrequency for exciting the fluorescent material, scanning the surfacefor discontinuities occurring in fluorescent radiation which correspondsto defects in the vessel, and providing an indication of [56] ReferencesCited the existence of such a discontinuity The selected sur UNITEDSTATES PATENTS faces, in particular, comprise helically formed threadsAllEJUlgCl' X and the top urfaces of s crew top beverage An 3,675,015 71972 Gelb 250 302 apparatus in accordance with the invention is pm videdfor effecting the examination of a glass vessel.

23 Claims, 17 Drawing Figures 20 Z? 24 25 J\ ..A ,A

was Rwss 5p FILL/1V6 52 & 34 {I 29 64 6 2.9 rt t/h fl flfl flfl fl/l flflflflfl lflfl at 4/ a PATENTEDAUG 13 I974 minors E- I I 5- Wm w II n IPATENTEDAUB 1 3 I974 FROM DETECTOR I32 'PIHIHPL IFAER mason;

CONTROL MORY CONTROL END OF ROTH T/ON v REJECT METHOD AND APPARATUS FORTHE EXAMINATION OF ARTICLES FOR DEFECTS This invention relates generallyto an improved method and apparatus for the examination of articles byfluorescent techniques. The invention relates more particularly to animproved method and apparatus for the detection with fluorescenttechniques of defects occurring in glass beverage vessels and the like.

Fluorescent examination of articles for flaws or defects therein hasprincipally been accomplished with a known technique referred to as thepenetration technique. Examination with this technique is accomplishedby coating a surface of an article with a fluorescent material, rinsingthe fluorescent material from the surface and then irradiating theobject with ultraviolet light. Defects in the article, such as hairlinecracks and similar flaws which extend from the surface of the object andwhich are otherwise not visible to the naked eye, trap and retain thefluorescent material. Upon irradiation, the entrapped materialfluoresces and reveals the presence and extent of any defects.

Various other procedures for the fluorescent examination of glassvessels are known. One such procedure requires the fabrication of avessel being examined from a fluorescent material. Upon irradiation ofthe vessel, smooth surfaces of the vessel wall cause a uniform internalreflection of fluorescent radiation and a resulting confinement of theradiation within the vessel wall. The existence of a flaw howeverinterrupts the uniformity of reflection and permits radiation to emanatefrom the flaw. This reflected radiation which escapes from the wall isthen detected.

Another fluorescent examination technique has been employed forinspecting the interior of glass beverage bottles for residue andforeign objects. The interior of the bottle is washed with a fluorescentliquid and is then rinsed. Irregular surfaces of particles or a residueremaining in the bottle will retain or trap a portion of the fluorescentmaterial and reveal its presence upon irradiation with ultravioletlight.

These known flourescent examination techniques can be impractical andcostly, particularly when employed for beverage bottle examination. Thepenetration technique, for example, necessitates the removal or rinsingof the fluorescent material from the article before the existence of thedefect can be sensed. There are instances however in which it is notfeasible to rinse or remove the major portion of the fluorescentmaterial. This is true in the recycling of glass beverage bottles. Alarge number of present day glass beverage bottles include integrallyformed threads which engage a mating threaded bottle cap. Examination ofthe top surface of the bottle and the threads of a recycled bottle fordefects is important for several reasons. The upper portion of a bottleoften comes in contact with a users mouth and sharp edged voids andflaws can cause personal injury to the user. In addition, a defectivebottle top surface can cause an incomplete seal resulting in the loss ofcarbonation and entry of bacterial growth when beverages contain sugar.In practice, large numbers of bottles are examined and in order to beeconomically feasible, the handling and examination of the bottlesshould occur at a relatively high rate such as, for example, bottles persecond. However, it is found that recycling equipment which is providedfor washing and rinsing the bottles and for conveying bottles betweenvarious operating stations at these relatively high rates can itselfcause damage to the bottles. While, in comparison with the total numberof damaged returned bottles, this process results in a relatively lowpercentage of damage to bottles, nonetheless, the risk of personalinjury to a user from a defective bottle thread dictates that alldefective bottles be detected and discarded.

lt is therefore preferable to examine the bottle threads after theprincipal recycling and cleaning steps have been performed andimmediately before refilling of the bottles. At this stage of theprocess, however, fluorescent examination by techniques such as thepenetration technique which provides for coating with a fluorescentmaterial and then rinsing the material from the surface of the bottlewill substantially reduce the reprocessing rate and can render thereprocessing examination costly. Alternatively, the fabrication ofbottles from a fluorescent material is limiting and can be prohibitivelyexpensive. Furthermore, detection arrangements employed with priorfluorescent sources for the examination of articles have suffered fromreflections and refractions which interferred with the accuracy ofdetection.

Accordingly, it is an object of this invention to provide an improvedmethod and apparatus for inspecting articles by fluorescent examinationtechniques.

Another object of the invention is to provide an improved method andapparatus for examining an article by fluorescent techniques wherein afluorescent material whjch is deposited upon a surface of the articleremains on the surface during the examination.

Another object of the invention is to provide a method and apparatus forfluorescent examination of an article wherein a fluorescent materialwhich is deposited upon the article for purposes of examination of thearticle remains on the article after examination.

Another object of the invention is to provide an improved method offluorescent examination of articles wherein the article acts as afluorescent light source and having an improved defect detectionarrangement which is substantially nonsusceptible to reflection ofincident exciting light.

Another object of the invention is to provide a method of fluorescentexamination of articles which are compatible with digital informationhandling techniques.

Still another object of the invention is to provide a relatively highspeed and relatively low cost method and apparatus for the examinationof screw threads and upper bottle surfaces on a screw top glass bottle.

A further object of the invention is to provide an improved method andapparatus for the examination of recycled glass bottles for defectswhich may occur in the bottle.

In accordance with the general features of this invention, a fluorescentmaterial is deposited on the surface of an article being examined and isinhibited from introduction into voids or defects extending into thearticle from the surface. The article surface is subsequently irradiatedat a frequency for exciting the deposited fluorescent material anddiscontinuities occurring in fluorescent radiation along the surfacecorresponding to defects in the surface are detected and indicated.

In accordance with more particular features of this invention, a methodfor examining the upper part of a glass vessel for defects comprises thesteps of applying a fluorescent material to selected surfaces of theupper part of the vessel with an applicator having a firmness whichinhibits entry of the fluorescent material into voids or defectsexisting in the article and extending into the vessel from the selectedsurfaces, irradiating the coated surface with light having a frequencyfor exciting the fluorescent material, scanning the surface fordiscontinuities occurring in fluorescent radiation which correspond todefects in the vessel, and providing an indication of the existence ofsuch a discontinuity. The selected surfaces, in particular, comprise theintegrally formed threads and top surface of a screw top beveragebottle.

In accordance with more particular features of the invention, thefluorescent material comprises a substance which is adapted for humanconsumption and which may remain on the bottle after examination.

These and other objects and features of the invention will becomeapparent with reference to the following specification and to thedrawings wherein:

FIG. I is a flow chart illustrating the process of this invention;

FIG. 2a is an elevation view of an upper portion of a screw thread glassbeverage bottle illustrating an integrally formed non-defective screwthread and top bottle surfaces.

FIG. 2b is a plan view of the bottle of FIG. 2a;

FIG. 3a is an elevation view of an upper portion of a screw thread glassbeverage bottle illustrating an integrally formed defective screw threadand a defective top bottle surface;

FIG. 3b is a plan view of the bottle of FIG. 3a;

FIG. 4 is a diagram of a bottle recycling and examination apparatusconstructed in accordance with features of this invention;

FIG. 5 is a side view of an apparatus for depositing a fluorescentmaterial on a screw thread surface and a top bottle surface of a glassbeverage bottle;

FIG. 6 is a view taken along line 6-6 of FIG. 5;

FIG. 7 is a schematic plan view of a part of an examination station ofthe apparatus of FIG. 4;

FIG. 8 is a schematic elevation view of another part of the examinationstation of the apparatus of FIG. 4;

FIG. 9 is a view of an upper portion of a screw top glass bottleillustrating the thread configuration for different orientations of thebottle with respect to a detector means as the vessel is rotated aboutits axis;

FIG. 10 is a view taken along lines 10l0 of FIG. 7 and illustrating anaperture disc of the detection means of FIG. 7;

FIG. 11 is a view taken along line 11l1 of FIG. 7 and illustrating thesurface of a segmented photodetector upon which fluorescent radiationfrom the bottle impinges;

FIG. 12 is a view illustrating an alternative form of photodetector;

FIG. 13 is a schematic diagram in block form ofa circuit means fordigitally sensing and indicating a defect in a bottle under examination;

FIG. 14 is a schematic diagram in block form of an alternative circuitmeans for digitally sensing and indicating a defect in a bottle underexamination; and

FIG. 15 is a schematic diagram in block form of an alternative circuitmeans for providing analog sensing and for indicating a defect in abottle under examination.

FIG. 1 illustrates the steps employed in accordance with features ofthis invention. While the present invention will be described withrespect to the recycling of glass bottles, the invention is alsoapplicable to the examination of newly manufactured bottles as well asto the examination of other types of articles. Bottles for recycling arederived from a source 18 and are conveyed in sequence to a cleaning andrinsing station 20, a coating station 22 at which an upper portion ofthe bottles is coated with a fluorescent material, and to an examinationstation 24 where the bottles coated with fluorescent material areexamined for defects. When a determination is made that a bottle isdefective, the bottle is discarded. The discard occurs by bypassing thebottle to a discard conduit represented by line 25 before the bottle isfilled at a subsequent station 26. Alternatively, and in view of therelatively low proportion of defective bottles encountered, it is lesscostly at times in terns of equipment and processing rate to fill adefective bottle and then discard the bottle. Non-defective bottleswhich are filled at station 26 are conveyed to a station 28 where theyare capped. The bottles are then collected for distribution.

FIG. 4 illustrates an apparatus for carrying out the described bottlerecycling process. Recycled bottles 20 are transported by a conventionalbottle conveying means 30 from the source 18 (FIG. 1) to the cleaningand rinsing station 20 at which location the bottles are scoured underpressure with a detergent wash. The wash is derived from a source andpump means 32 and is introduced into the bottles by a suitable conduitmeans 34. The detergent is pumped from the bottle through the conduit 34at this location and the bottle then is conveyed to a rinsing location.A clear rinse is derived from a rinse source and pump means 36 at therinsing station and is pumped into and then flushed from the bottle atthis location. The equipment for performing the washing and rinsingsteps is conventional.

As indicated hereinbefore, recycling of bottles is preferablyaccomplished at a relatively high transport rate. For example, thebottles are in practice stepped past a station at a rate of about 10bottles per second. Because of this relatively high rate and thepossibility of damage to the bottles from the equipment itself, it ispreferable to examine the bottles for defects after cleaning andimmediately prior to the beverage filling step.

The fluorescent material coating station 22 provides for depositing afluorescent material on the top surface 37 of the bottle wall (FIG. 2a),on the outer surface or ridge 38 of the helical screw threads, and on acap locking shoulder segment 39 while inhibiting deposition of thematerial in voids or defects which may exist in the top surface 37 inthe screw thread 38, in voids or defects in the shoulder segment 39, andin valleys and spaces 40 extending between the threads. The fluorescentmaterial coating station of FIG. 4 is shown to include a rotatableturntable 41 which is mounted to a drive shaft 42. The drive shaft 42 iscoupled by a drive belt 44 to a drive shaft of a motor 46. A bottle 29is stepped onto the turntable 44 and is rotated at a predetermined speedupon energization of the motor 46. Although the turntable 41 isillustrated as supporting a single bottle for rotation, multiunitturntables can be provided which are adapted for rotating a plurality ofbottles simultaneously. The coating station 22 further includes areservoir 48 containing a fluorescent material 50 which is conveyed bygravity feed, for example, through a conduit 52 to a transfer applicator54. The transfer applicator 54 is rotatably mounted on a shaft 56 and ispositioned in contact with an applicator 58 which is similarly rotatablymounted on a shaft 60. These shafts are coupled by a drive belt 62 to adrive shaft of a motor 46. The applicator 58 is positioned forcontacting selected surfaces 37, 38 and 39 of the bottle being coatedand is driven at a rate for providing that the outer surface of theapplicator 58 and these selected surfaces of the bottle are transportedat the same rate. Stepping of the conveyor 30 and energization andde-energization of the drive motor 46 is controlled and synchronized byconventional means, not illustrated.

Reference is made to FIGS. 2, 3, 5 and 6 for a more detailed view anddescription of the applicator and the bottle 29. While there isillustrated a screw cap bottle closure, the invention is equallyapplicable to twist off, crown caps, and other forms of bottle closures.

v An upper part of a bottle 29 is shown to include an integrally formedhelically configured glass screw thread 72 having a thread startingsegment 74 and a thread terminating segment 76 which terminates at thecap shoulder 39. The valley areas or spaces 40 extending between thesegments of the screw threads are generally planar. In comparison withthe non-defective bottle of FIG. 2a, FIG. 3a illustrates a top surface37 having a chipped out defect 79, a screw thread 72 having defects 80and 81 and a shoulder 39 having a defect 81. These defects and flaws canhave relatively sharp edges and can result in personal injury. Inaddition the flaw 79 in the top surface 37 can cause the loss of a sealbetween a cap and the bottle and result in a loss of carbonation in thecase of carbonated beverages and in the growth of bacteria with sugarcontaining beverages.

In coating the selected surfaces 37, 38 and 39, it is important forproper detection of defects to inhibit the coating of the valley bottlesurface 40 and the defects 79, 80, 81 and 82. The applicator isdimensioned so that the applicator body itself cannot enter these voidsor valleys. It is further achieved by providing an applicator 58 whichis formed of a material which is capable of transporting the fluorescentmaterial on its surface yet exhibits a stiffness which, when in contactwith selected surfaces will not extend into voids or defects and willnot contact the surface 40. One such suitable applicator comprises acylinder 58 which is formed of rubber. Suitable rubbers comprise butyl,styrene butadiene, polybutadiene, polyisoprene and natural rubber.Another suitable applicator comprises a cloth faced rubber inking pad.The applicator 58 (FIG. 5) is generally cylindrically shaped andincludes a segment 83 of relatively larger diameter than another segment84. A lower surface 85 of the segment 83 extends over, contacts anddeposits the fluorescent material 50 on the bottle top surface 37. Anouter surface of the segment 84 contacts and deposits fluorescentmaterial on the ridge or edge surface 38 of the thread 72 and on theshoulder 39. The transfer applicator 54 is fabricated of a materialwhich is capable of receiving the fluorescent material 50 from thereservoir 48 and applying it by surface contact to the lower surface ofthe segment 83 and to the outer surface of the segment 84 of theapplicator 58. One such material for handling a liquid fluorescentmaterial comprises relatively soft sponge rubber.

As indicated, the valley surfaces 40 preferably should not be coatedwith the fluorescent material. Coating of this surface undesirablyincreases the complexity of the detection means as will become apparentfrom a consideration of particular detector means, hereinafter. However,the planar surface 40 as well as other planar surfaces on similar ordifferent articles may be coated with the fluorescent material when thedetector means is adapted for an analysis of this surface. With respectto the detector means discussed hereinafter, this can be accomplished bypresetting a counter to an appropriate count or by establishing adigital signature for a nondefective article surface.

The fluorescent material 50 preferably exists in the liquid statealthough powdered fluorescent materials may also be coated in accordancewith this invention. The fluorescent material employed for coatingrecycled beverage bottles preferably comprises a substance which issuitable for human consumption and thereby advantageously eliminates anypersonal hazard and the need for washing of the material from the coatedsurfaces after the detection step. While a large number of fluorescentsubstances existing in the liquid state and which are suitable for humanconsumption are known, liquids comprising solutions of a vehicle orsolvent and relatively small concentrations of quinine in particularhave been found to be suitable for this application. The liquid maycomprise any suitable solvent for quinine such as sodium alginate andwater. A carbonated water beverage containing quinine and sold under thetrade names of Quinine Water distributed by the Schwepps Corporation anda similar beverage distributed by the Cott Corporation comprises aliquid fluorescent material suitable for human consumption. Othersuitable materials which need not be rinsed are eosin in water, esculinin water or alcohol, and fluorescin in water. In addition, in thoseinstances when it is practical to rinse the coated material from thearticle other suitable fluorescent materials comprise anthrocene inalcohol, naphthalene-red in alcohol, resorsin blue in water andrhodamine in water.

After coating of selected surfaces, a bottle is transported by theconveyor 30 from the turntable 41 to the examination station 24. At theexamination station 24, the bottle is rotated past a stationary sensingmeans, illustrated in FIGS. 7 and 8, which detects discontinuities influorescent radiatin along the length of the surface being examined. Thesensing station is shown in FIG. 4 to include a turntable 96 which ismounted on a rotatable drive shaft 98. The drive shaft 98 is coupled bya drive belt 100 to the drive shaft of the electric motor 65 causingrotation at a predetermined speed of a bottle 29 which is positioned onthe turntable.

The discontinuity detection means of FIG. 7 includes means forirradiating the upper part of a bottle 29 and for detecting adiscontinuity in the fluorescent radiation from the selected surface asthe bottle is rotated past the sensing station. The radiation meanscomprises an ultraviolet light source 106 from which a light beam 107 isprojected through a slit 108 in an aperture plate 110. The slit 108 hasa principal dimension extending in a direction substantially parallel toa longitudinal axis 112 of the bottle 29. The light beam 107 istransmitted through a filter 114 which is adapted for passing withminimum attenuation those light components occurring in the UV band andfor eliminating visible light. The light beam 107 is focused by a lens116 onto a segment of the upper bottle extending from the shoulder 39 toand including the upper surface 37. Scanning for discontinuities isprovided by rotating the bottle and sequentially positioning segments ofthe bottle for impingement by the light beam.

Coated surfaces upon which the beam 107 impinges fluoresce and thebottle thus acts as a light source. This fluorescent radiation,represented by the beam 120, is focused by a lens 122 on a slit 126 inan aperture plate 128. A filter 129 is positioned in the path of thisbeam and is adapted for restricting the transmission of light to thosecomponents occurring within the light spectrum of the fluorescingmaterial and for eliminating UV light. The use of the filters 114 and129 greatly enhances the signal noise characteristic of the detectionmeans. A photodetector 130 is positioned behind the plate 128 and isaligned with the slit 126. An electrical signal having an amplitudeproportional to the intensity of the'impinging light beam is generatedby the photodetector and is coupled to a scanning and preamplifyingmeans 131 discussed hereinafter. With the exceptions enumeratedhereinafter, a non-defective bottle generates substantially continuousfluorescent radiation and provides a substantially continuous outputsignal from the photodetector as the bottle is rotated. However, defectsin the selected surfaces result in an interruption in fluorescentradiation and a corresponding interruption in the continuity of theelectrical signal. The amplified signal is coupled, as indicated indetail hereinafter, to circuit means for an analysis of thephotodetector signal and a determination and indication of the existenceof a defect in the bottle.

Fluorescent radiation from the top surface 37 is similarly sensed, asillustrated in FIG. 8, by focusing the fluorescent radiation on aphotodetector 132. The photodetector 132 is positioned behind a slit 133in an aperture plate 134. The beam 136 of fluorescent radiation isfocused by a lens 137 onto the detector 132. An optical filter 138having transmission characteristics for passing the spectrum generatedby the fluorescent radiation and similar to that of filter 129 of FIG. 7is positioned in the path of the beam 136. An output signal from thedetector 132 is coupled to a preamplifier 139 for amplification andcoupling to circuit means for analyzing the detector signals.

The operation of the error determination circuit means of FIGS. 13, 14and will be more fully appreciated by a consideration of the characterof the fluo-' rescing surfaces under examination. FIG. 10 which is aview of the output aperture plate 128 and the slit 126 formed thereinillustrate that the coated fluorescent material is positioned at threelocations along the length of the slit. An upper shaded segment 140represents fluorescent radiation emanating from the uppermost threadsegments while the segments 14] and 142 represent fluorescent radiationemanating respectively from a lower thread segment located at adifferent vertical position on the bottle and from the shoulder segment39. The pattern illustrated in FIG. 10 represents the fluorescentradiation pattern presented to the detector 130 for one rotationalposition of a bottle. As the bottle is rotated, the helicalconfiguration of the thread 72 causes the thread segments 140 and 141 toassume different vertical locations in the slit. The fluorescentsegments 140 and 141 therefore appear to be moving vertically within theslit. Since a bottle is rotated at a substantially constant angularvelocity, the segments and 141 will appear to move in a verticaldirection at a substantially uniform rate. However, at the threadstarting segment 74 (FIG. 2) and at the thread terminating segment 76,discontinuities will appear to occur. The discontinuities represent therotational orientation of the bottle and are not indicative of a defectin the screw thread. They must be accounted for in the analysis of thephotodetector output. In FIG. 9, the slit 126 is superimposed on thescrew threads in order to illustrate the variations in the screw threadpatterns which will be presented to the photodetector at differentrotational orientations of a bottle about its longitudinal axis. Theshoulder segment 142 and the flat top surface segment 37 do not exhibita variation along the length of the slits 126 and 132, respectively, andthe fluorescent radiation emanating from these slits will remain atstationary locations within their respective slits. It is noted that thepresentation of the fluorescing surfaces represents bits of informationwhich conveniently lend themselves to analysis by digital techniques.

Defects which may occur in the selected surfaces being examined can havevarying widths along the length of the thread, depending upon the typeand severity of the defect. Typically, bottles having defects on theorder of one-half millimeter or greater along the length of the surfacein the general direction of rotation are considered potentiallydangerous and should be detected and discarded. The width of the slit ispreferably about /2 millimeter at the bottle top and the length of theslit 126 extends from the bottom of the shoulder 39 to the surface 37.The length of the slit 133 extends for about the thickness of the bottlewall near the surface 37.

FIG. 13 illustrates a circuit arrangement for handling data provided bythe detectors 130 and 132. The photodetectors 130 and 132 are segmentedalong their length into a plurality of insulated segments and 151,respectively, each of which provides an independent output voltage on anassociated output line 152 and 153 respectively. The output of thephotodetectors is then scanned by a high speed electronic switch 154which cyclically and sequentially couples each of the photodetectorsegments to a preamplifier 156. The switching operation of theelectronic switch 154 is controlled by a control and synchronizing means158 which also synchronizes an output signal from a pulse generator 160.The pulse generator 160 provides an output pulse which is coupled to anAND gate 162 along with the output from the preamplifier 156. Theoccurrence of an output signal from the preamplifier 156 indicates thatthe segment which is coupled to the preamplifier at a particular pointof time in the scanning cycle by the electronic switch 154 is beingimpinged by fluorescent radiation from a segment of the coated surface.Upon the occurrence of an output signal from the preamplifier 156, thepulse generator 160 will enable the AND gate 162 and provide a pulseoutput to a preset countdown counter 164. This counter is preset to avalue representative of the number of counts which would be provided bya bottle having no defects in the surface examined and therefore nodiscontinuities in fluorescent radiation as the bottle is rotated. Thispreset count is adjusted to account for the discontinuities caused bythe thread segments 74 and 76 as discussed hereinbefore. The initialrotational orientation of a bottle on the table 96 (FIG. 4) need notproceed from a same reference location on each bottle in this form ofoperation since the number of counts for a non-defective bottle areknown and since only the total count is being examined and compared withthe total count of a nondefective bottle. Initiation and termination ofrotation of a bottle at the examination station is controlled by thecontrol and synchronizing means 158 which provides an output controlsignal for controlling excitation of the motor 65 (FIG. 4) and providesan output signal, which indicates termination of rotation and of theexamination, to an AND gate 166. The rotation of a non-defective bottlewill result in the countdown of the preset counter to a predeterminedcount such as a binary zero state. An absence of one or more pulses tothe counter 164 will result in a binary count differing from thepredetermined final count and will enable an AND gate 166 and initiate abottle reject operation. The reject operation comprises for example theactuation of a mechanical gate, not shown, which diverts the transportof a defective bottle either before or after filling with a beverage toa discard bin.

FIG. 14 illustrates an alternative form of circuit means for digitallyexamining the condition of coated selected surfaces of a screw topbottle. The photodetector 130 is, similiar to FIG. 13, divided into aplurality of segments 150, each of which is mutually insulated and eachof which has an output line 152 for coupling an associated photodetectorsegment to a preamplifier strip 168. The preamplifier strip includes aplurality of preamplifing stages 170 equal in number to thephotodetector segments 150 and each of which is associated with one ofthe photodetector segments. This arrangement provides for a binarypresentation in parallel of the state of each of the photodetectorsegments 150'as the bottle rotates. This information is coupled inparallel through an input/output terminal 172 to the arithmatic section174 of a small scale wired program computer. The binary informationpresented by the photodetector 130 at each rotational position of thebottle is coupled to the computer and is stored in a memory system 176.There is previously stored in the memory system 176 a pattern,configuration or signature of a bottle known to be non-defective. Thisinformation or signature is provided by examining a bottle known to benon-defective in order to generate signal patterns which are then storedas reference data. Data from a bottle under examination and which istemporarily stored in memory 176 is then transferred to the arithmeticunit 174 for comparison with the signature" or data from a non-defectivebottle.

It is noted that the data derived from a bottle under examination isstored without respect to a predetermined orientation. In order tocompare the sample data with the reference data, the sample data isconvolved with the reference data. The results of each signal are addedand the arithmatic unit 174 searches for a maximum value. A startingpoint for comparison is then set equal to the sample position of maximumvalue. Having thus established the start position, the reference dataand the sample are compared signal by signal and any differences can beassociated with bottle defects.

FIG. 15 illustrates an analog detection circuit arrangement fordetecting discontinuities in fluorescent radiation from selectedsurfaces. A photodetector suitable for use with the arrangement of FIG.15 is illustrated in FIG. 12. This photodetector comprises a unitarystrip 180 which is exposed to fluorescent radiation along the entirelength of the aperture slit. The total in stantaneous output power ofthe photodetector is proportional to the area of the fluorescentradiation impingement on the photodetector strip. As the bottle isrotated, the output power will vary in accordance with the area of thecoated surface which provides fluorescent radiation. A non-defectivebottle will provide substantially smooth and gradual changes in outputpower. A defective bottle however will cause relatively sharpdiscontinuities in the power level which are detected by the arrangementof FIG. 15. In addition, the discontinuities of the thread segments 74and 76 will cause relatively sharp discontinuities in the output powerlevel. During one revolution of a non-defective bottle, there will betwo relatively short discontinuities in the output power.

The output from the photodetectors and 132 which are arranged as thenonsegmented unit of FIG. 12 are coupled to preamplifiers 181 and 182,respectively. Signal outputs from these preamplifiers are in turncoupled to differentiating and wave shaping circuit arrangements 183 and184, respectively. Since the change in the power output level from thephotodetectors for a non-defective bottle is relatively smooth andgradual, there will be no output from the differentiating and waveshaping circuit arrangements 183 and 184. However, the relatively sharpdiscontinuities created by the thread segments 74 and 76 will result intwo discontinuities and thus two output pulses from the differentiatingand wave shaping circuit 183. This output is coupled through an OR gate185 to a binary counter 186. A control means 187 controls the rotationof the vessel by initiating and terminating the energization of therotating motor and in addition resets the counter 186 to a binary zero.During a rotational cycle of a nondefective bottle, the counter 186 willhave a count of binary two, (i.e., 010). An AND gate 188 is accordinglydisabled and a reject signal is not generated. However, the existence ofdefects in the bottle surfaces being examined will result in sharpdiscontinuities in the fluorescent radiation and wil result in one ormore additional pulses creating a 010. This output signal along with theend of rotation signal from the control means 186 results in a rejectsignal output from the AND gate 188.

Although this specification has specifically described fluorescentexamination techniques with respect to recycling of screw thread glassbottles, the invention is equally applicable to the examination ofdefects in other types of bottles. For example, this invention mayadvantageously be utilized for an inspection of crowns on non-threadedbottle cap types of bottles. Newly manufactured as well as recycledvessels can be examined with this invention. Furthermore, the techniquesdescribed are applicable to the detection of surface defects in otherarticles.

There has thus been described an improved method and apparatus forexamining articles for defects existing therein. These defects areadvantageously detected by coating the surface under examination with afluorescent material and inhibiting entry of the material into voids ordefects, irradiating the coated surface causing fluorescence of thecoated material and detecting discontinuities in the fluorescentradiation as the article is rotated.

While there has been described particular embodiments of the invention,it will be understood that modifications may be made thereto withoutdeparting from the spirit of the invention and the scope of the appendedclaims.

What is claimed is:

1. A method for examining articles for the detection of voids whichextend into the article from a surface of the article comprising thesteps of:

Depositing a material on the surface of an article being examined andinhibiting the introduction of the material into voids extending intothe article from the surface, said material adapted to fluoresce whenirradiated with light energy of a predetermined spectrum;

Irradiating the surface of said article at the predetermined spectrumfor exciting the fluorescent material and causing fluorescent radiationtherefrom; and,

Detecting discontinuities occurring in fluorescent radiation along thesurface thereof corresponding to voids in the surface.

2. The method of claim 1 wherein said fluorescent material is depositedon the surface and inhibited from introduction into the voids byapplying the material with an applicator having a surface hardness whichinhibits the applicator surface from extending into a void existing inthe surface of the article.

3. The method of claim 2 wherein said coated surface is irradiated byscanning the coated surface with a light beam thereby causing sequentialfluorescent radiation from the coated surface at a radiation detectionmeans.

4. The method of claim 3 wherein said coated surface is scanned byproviding relative motion between the light beam and the article.

5. The method of claim 4 wherein relative motion is provided betweensaid article and said light beam by transporting said article about anaxis of the article past a stationary light beam.

6. The method of claim 3 including projecting the light beam at thecoated surface through an optical filter which transmits light of alimited frequency spectrum for exciting the coated material andprojecting the fluorescent radiation at the detection means through anoptical filter which transmits light of a limited frequency spectrumcorresponding to the spectrum of fluorescent radiation of the excitedfluorescent material.

7. The method of claim 6 wherein said fluorescent radiation is projectedat said detection means and said detection means is scanned forgenerating electrical indications in digital form of the occurrence orthe absence of fluorescent radiation from a selected surface of thearticle.

8. The method of claim 2 wherein said coated material comprises asolution of quinine in a solvent.

9. The method of claim 2 wherein said applicator is formed of rubber.

10. A method for examining a glass vessel for defects which extend froma surface of the vessel into the vessel comprising the steps of:

Applying a fluorescent material to a selected surface of the vessel withan applicator having a surface dimension and firmness which inhibit theentry of the applicator surface and the fluorescent material into a voidexisting in the surface;

Irradiating the coated surface with light having a frequency spectrumfor exciting the fluorescent material and causing fluorescent radiationtherefrom;

Scanning the coated surface by providing relative motion between thecoated surface and said irradiating light;

Detecting discontinuities occurring in fluorescent radiation whichcorrespond to a void in the vessel surface; and,

Providing an indication of the existence of the discontinuity.

11. The method of claim 10 wherein said vessel comprises a glass bottleand said selected surface comprises a top surface of the bottle.

12. The method of claim 10 wherein said vessel comprises a glass bottleand said selected surface comprises a helically shaped integral glassthread formed in an upper part of the bottle and which is adapted forengaging a closure cap for the bottle.

13. The method of claim 12 wherein said selected surface includes ashoulder segment integrally formed in an upper part of the bottle forsealing a bottle cap thereto.

14. A method for examining a glass beverage bottle for defects or flawsin an upper portion of the bottle, said upper portion including anintegrally formed top wall surface and a helically shaped thread forengaging a closure member for the bottle comprising the steps of:

Coating a surface of the thread with a fluorescent material which isdeposited on said surface by an applicator having a surface area andstiffness which inhibits the entrance of the applicator and theintroduction of coating material into voids or flaws which extend fromthe surface of the thread into the body of the thread;

Projecting a narrow rectangular shaped beam of ultraviolet light at saidupper portion of said bottle thereby causing fluorescent radiation toemanate from coated surfaces located within the relatively narrow areaof beam impingement;

Rotating the bottle about a longitudinal axis thereof,

past the light beam;

Directing the fluorescent radiation at a photo detection means forgenerating an electrical signal representative of beam impingement uponsaid photo detection means; and,

Analyzing an electrical output signal from said photo detection meansfor sensing discontinuities occurring in fluorescent radiation from saidcoated surface which correspond to a defect in the surface.

15. The method of claim 14 wherein said rectangular shaped beam isprojected at said bottle for providing that a relatively longerdimension of said rectangular shaped beam is generally parallel to alongitudinal axis of said bottle.

16. The method of claim 15 wherein said photo detection means includes aphotodetector which is segmented into a plurality of photo detectorelements and said elements are sequentially scanned.

17. An apparatus for detecting surface voids existing in an articlecomprising:

Means for depositing a fluorescent material on a selected surface of anarticle being examined and for inhibiting the introduction of thematerial into a void extending into the article from said surface;

Means for irradiating said coated surface at a frequency for excitingthe deposited fluorescent material thereby causing fluorescent radiationfrom said surface;

and,

Means for detecting a discontinuity occurring in fluorescent radiationalong the surface corresponding to a void in the surface.

18. The apparatus of claim 17 wherein said fluorescent materialcomprises a solution of quinine in a vehicle.

19. An apparatus for examining the upper part of a glass vessel forvoids occurring therein comprising:

Means for applying a fluorescent material to selected surfaces of theupper part of the vessel, said means including an applicator body incontact with said surface and having a dimension which is generallylarger than the voids occurring in the vessel and having a surfacehardness for inhibiting the entry of said applicator surface and theintroduction of said material into said voids;

Means for scanning the coated surface with light having a frequency forexciting the fluorescent material; and,

Means for detecting discontinuities in fluorescent radiationcorresponding to voids in the surface.

20. The apparatus of claim 19 wherein said means for scanning saidselected surface and detecting discontinuities in fluorescent radiationcomprises a source of ultraviolet light, means for providing relativemotion between said light source and said vessel, means for projectingultraviolet light from said source at said selected surface through anoptical filter which transmits ultraviolet light and inhibits thetransmission of visible light, a photodetector, means for projectingfluorescent radiation at said photodetector through an optical filterwhich transmits light within a limited frequency spectrum correspondingto the spectrum of the fluorescent radiation, said photodetectorproviding an output signal corresponding to voids in the selectedsurface.

21. The apparatus of claim 20 wherein said photodetector comprises aplurality of segmented photodetector elements and means are provided forsequentially scanning each of said elements for sensing the occurrenceor non-occurrence of an electrical signal at said element.

22. The apparatus of claim 19 wherein said applicator is formed ofrubber.

23. A method for examining recycled glass vessels comprising the stepsof:

Conveying the vessels to a washing and rinsing station;

Washing and rinsing the vessels;

Conveying the vessels from the washing and rinsing station to a coatingstation;

Applying a fluorescent material to a selected surface of the vessel withan applicator having a surface dimension and firmness which inhibits theentry of the applicator surface and the fluorescent material into voidsor defects existing in the surface;

lrradiating the coated surface with light having a frequency spectrumfor exciting the fluorescent material and causing fluorescent radiationtherefrom;

Scanning the coated surface by providing relative motion between thecoated surface and said irradiating light;

Detecting discontinuities occurring in fluorescent radiation whichcorrespond to a void in the vessel surface;

and

Discarding the vessels in which voids in the vessel surface weredetected.

1. A method for examining articles for the detection of voids whichextend into the article from a surface of the article comprising thesteps of: Depositing a material on the surface of an article beingexamined and inhibiting the introduction of the material into voidsextending into the article from the surface, said material adapted tofluoresce when irradiated with light energy of a predetermined spectrum;Irradiating the surface of said article at the predetermined spectrumfor exciting the fluorescent material and causing fluorescent radiationtherefrom; and, Detecting discontinuities occurring in fluorescentradiation along the surface thereof corresponding to voids in thesurface.
 2. The method of claim 1 wherein said fluorescent material isdeposited on the surface and inhibited from introduction into the voidsby applying the material with an applicator having a surface hardnesswhich inhibits the applicator surface from extending into a voidexisting in the surface of the article.
 3. The method of claim 2 whereinsaid coated surface is irradiated by scanning the coated surface with alight beam thereby causing sequential fluorescent radiation from thecoated surface at a radiation detection means.
 4. The method of claim 3wherein said coated surface is scanned by providing relative motionbetween the light beam and the article.
 5. The method of claim 4 whereinrelative motion is provided between said article and said light beam bytransporting said article about an axis of the article past a stationarylight beam.
 6. The method of claim 3 including projecting the light beamat the coated surface through an optical filter which transmits light ofa limited frequency spectrum for exciting the coated material andprojecting the fluorescent radiation at the detection means through anoptical filter which transmits light of a limited frequency spectrumcorresponding to the spectrum of fluorescent radiation of the excitedfluorescent material.
 7. The method of claim 6 wherein said fluorescentradiation is projected at said detection means and said detection meansis scanned for generating electrical indications in digital form of theoccurrence or the absence of fluorescent radiation from a selectedsurface of the article.
 8. The method of claim 2 wherein said coatedmaterial comprises a solution of quinine in a solvent.
 9. The method ofclaim 2 wherein said applicator is formed of rubber.
 10. A method forexamining a glass vessel for defects which extend from a surface of thevessel into the vessel comprising the steps of: Applying a fluorescentmaterial to a selected surface of the vessel with an applicator having asurface dimension and firmness which inhibit the entry of the applicatorsurface and the fluorescent material into a void existing in thesurface; Irradiating the coated surface with light having a frequencyspectrum for exciting the fluorescent material and causing fluorescentradiation therefrom; Scanning the coated surface by providing relativemotion between the coated surface and said irradiating light; Detectingdiscontinuities occurring in fluorescent radiation which correspond to avoid in the vessel surface; and, Providing an indication of theexistence of the discontinuity.
 11. The method of claim 10 wherein saidvessel coMprises a glass bottle and said selected surface comprises atop surface of the bottle.
 12. The method of claim 10 wherein saidvessel comprises a glass bottle and said selected surface comprises ahelically shaped integral glass thread formed in an upper part of thebottle and which is adapted for engaging a closure cap for the bottle.13. The method of claim 12 wherein said selected surface includes ashoulder segment integrally formed in an upper part of the bottle forsealing a bottle cap thereto.
 14. A method for examining a glassbeverage bottle for defects or flaws in an upper portion of the bottle,said upper portion including an integrally formed top wall surface and ahelically shaped thread for engaging a closure member for the bottlecomprising the steps of: Coating a surface of the thread with afluorescent material which is deposited on said surface by an applicatorhaving a surface area and stiffness which inhibits the entrance of theapplicator and the introduction of coating material into voids or flawswhich extend from the surface of the thread into the body of the thread;Projecting a narrow rectangular shaped beam of ultraviolet light at saidupper portion of said bottle thereby causing fluorescent radiation toemanate from coated surfaces located within the relatively narrow areaof beam impingement; Rotating the bottle about a longitudinal axisthereof, past the light beam; Directing the fluorescent radiation at aphoto detection means for generating an electrical signal representativeof beam impingement upon said photo detection means; and, Analyzing anelectrical output signal from said photo detection means for sensingdiscontinuities occurring in fluorescent radiation from said coatedsurface which correspond to a defect in the surface.
 15. The method ofclaim 14 wherein said rectangular shaped beam is projected at saidbottle for providing that a relatively longer dimension of saidrectangular shaped beam is generally parallel to a longitudinal axis ofsaid bottle.
 16. The method of claim 15 wherein said photo detectionmeans includes a photodetector which is segmented into a plurality ofphoto detector elements and said elements are sequentially scanned. 17.An apparatus for detecting surface voids existing in an articlecomprising: Means for depositing a fluorescent material on a selectedsurface of an article being examined and for inhibiting the introductionof the material into a void extending into the article from saidsurface; Means for irradiating said coated surface at a frequency forexciting the deposited fluorescent material thereby causing fluorescentradiation from said surface; and, Means for detecting a discontinuityoccurring in fluorescent radiation along the surface corresponding to avoid in the surface.
 18. The apparatus of claim 17 wherein saidfluorescent material comprises a solution of quinine in a vehicle. 19.An apparatus for examining the upper part of a glass vessel for voidsoccurring therein comprising: Means for applying a fluorescent materialto selected surfaces of the upper part of the vessel, said meansincluding an applicator body in contact with said surface and having adimension which is generally larger than the voids occurring in thevessel and having a surface hardness for inhibiting the entry of saidapplicator surface and the introduction of said material into saidvoids; Means for scanning the coated surface with light having afrequency for exciting the fluorescent material; and, Means fordetecting discontinuities in fluorescent radiation corresponding tovoids in the surface.
 20. The apparatus of claim 19 wherein said meansfor scanning said selected surface and detecting discontinuities influorescent radiation comprises a source of ultraviolet light, means forproviding relative motion between said light source and said vessel,means for projecting ultraviolet light from said source at sAid selectedsurface through an optical filter which transmits ultraviolet light andinhibits the transmission of visible light, a photodetector, means forprojecting fluorescent radiation at said photodetector through anoptical filter which transmits light within a limited frequency spectrumcorresponding to the spectrum of the fluorescent radiation, saidphotodetector providing an output signal corresponding to voids in theselected surface.
 21. The apparatus of claim 20 wherein saidphotodetector comprises a plurality of segmented photodetector elementsand means are provided for sequentially scanning each of said elementsfor sensing the occurrence or non-occurrence of an electrical signal atsaid element.
 22. The apparatus of claim 19 wherein said applicator isformed of rubber.
 23. A method for examining recycled glass vesselscomprising the steps of: Conveying the vessels to a washing and rinsingstation; Washing and rinsing the vessels; Conveying the vessels from thewashing and rinsing station to a coating station; Applying a fluorescentmaterial to a selected surface of the vessel with an applicator having asurface dimension and firmness which inhibits the entry of theapplicator surface and the fluorescent material into voids or defectsexisting in the surface; Irradiating the coated surface with lighthaving a frequency spectrum for exciting the fluorescent material andcausing fluorescent radiation therefrom; Scanning the coated surface byproviding relative motion between the coated surface and saidirradiating light; Detecting discontinuities occurring in fluorescentradiation which correspond to a void in the vessel surface; andDiscarding the vessels in which voids in the vessel surface weredetected.